问题说明: 在获取数据库记录数据的时候, 通常返回的ArrayList集合, 没有了层次关系. 如果每次根据PID重新到数据库获取记录, 可以做到, 但有以下几个缺点:
1. 访问数据库记录次数随着记录的增多而增多
2. 由于需要多次访问数据库, 因此访问速度受影响
3. 需要数据库访问层的支持, 并对记录进行转化, 耦合性太强
4. 通用性不好, 每次需要一个新的类型列表, 就需要重新编写
解决方法: 我根据原有的树状结构算法代码, 编写一个通用的算法, 利用反射原理, 递归的对数据进行筛选.
这样只需要访问数据库一次, 然后就在内存中遍历, 而且适合于所有具有(PID, ID, Name)属性的实体类集合的排序.
public class CollectionHelper
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{
private static ArrayList Fill(int pID, int level, ArrayList list)
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{
ArrayList returnList = new ArrayList();
foreach(object obj in list)
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{
int typePID = (int)ReflectionUtil.GetProperty(obj, "PID");
int typeID = (int)ReflectionUtil.GetProperty(obj, "ID");
string typeName = ReflectionUtil.GetProperty(obj, "Name") as string;
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if(pID == typePID)
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{
string newName = new string('-', level * 4) + typeName;
ReflectionUtil.SetProperty(obj, "Name", newName);
returnList.Add(obj);
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returnList.AddRange(Fill(typeID, level+1, list));
}
}
return returnList;
}
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/**//// <summary>
/// 生成有层次结构的列表
/// </summary>
/// <param name="list">具有Name,ID,PID成员的任何集合</param>
/// <returns></returns>
public static ArrayList GetTreeItems(ArrayList list)
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{
return Fill(-1, 0, list);
}
}
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public sealed class ReflectionUtil
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{
private ReflectionUtil()
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{ }
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public static BindingFlags bf = BindingFlags.DeclaredOnly | BindingFlags.Public |
BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static;
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public static void SetProperty(object obj, string name, object value)
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{
PropertyInfo fi = obj.GetType().GetProperty(name, bf);
fi.SetValue(obj, value,null);
}
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public static object GetProperty(object obj, string name)
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{
PropertyInfo fi = obj.GetType().GetProperty(name, bf);
return fi.GetValue(obj,null);
}
}效果图如下
专注于代码生成工具、.Net/.NetCore 框架架构及软件开发,以及各种Vue.js的前端技术应用。著有Winform开发框架/混合式开发框架、微信开发框架、Bootstrap开发框架、ABP开发框架、SqlSugar开发框架等框架产品。
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